1950s conduit and modern electrical fittings

All the wiring in my new house is run in conduit which acts as the earth.
The conduit terminates in metal boxes approx 5"x"2.5" with the 15 amp faceplate fixed by four screws in the corners.
Is it possible to buy adaptor plates for these old style boxes or do I have to replace them and ,if so, how should the earth connection be secured.
Also, is it permissible to run earth connections from the terminals in new boxes to existing conduit runs fixed by an earthing strap?
TIA
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have
You would be better running new cables through the system to give you more scope in what you can connect. The old boxes you have should take a new back box inside it and let you fit new sockets.
Using the conduit as an earth is not the ideal either. If there are any breaks or loose fittings in the old installation, then the earth will effectively be broken at these points. They may show good connection when tested with a multi-meter, but if a short or other fault occurs, the break may not be able to pass the load safely and blow the fuse.
If you can get to all the junction boxes and socket ends, then pull three (red, black and green/yellow) new 2.5 mm PVC's through the old conduit to make a new ring main for the sockets at least, and make sure that the earth is properly bonded back the supply cable and into the fuse box (consumer unit).
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Hamish wrote:

Umm. IIRC steel boxes have the right sized holes to take those old conduits, if the thread is still present on the end, and useable..
There is a lot to be said for em. Fire in yer cables (not unusual with the rubber insulated cables they use) did not set the local mouse droppings, and house, on fire.
You CAN simply use em as earth, but heed BigWallops warnings.
IME, you can bodge the odd one if you know what you are doing, but if its a complete overhaul, you would be better served by ripping out the whole house wiring and redoing it with modern wiringts to modern standards and putting in a new consumer unit.
The original cable insulation is likely to be well perished, and the slightest disturbance may render it unservicable.
Re wire the lot, making as much mess as is needed, and get the plasterer in afterwards, and redecorate.
THEN you can install all the things like TV and cat 5 cables, LV spots and so on that will make it a far more useable and saleable house.
A house needs a major workover every 50 years. Time this one had it.

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Personally, I would re-use the main conduit runs where I could, even if I were extending the system. It is really hard to put a nail through steel conduit.

Or, in the case of electrics, a complete re-wire when the cable reaches the end of its life. A 1950s house that still has 15A sockets is probably about 30 years overdue for its first re-wire.
Colin Bignell
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50s conduit will be imperial, and I'm not sure where you'd get suitable boxes or backing rings etc. Also, I'd guess the originals will be proper conduit boxes where the conduit screws into a collar. They will be impossible to remove without damage, IMHO.
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I'm surprised you don't want extra sockets, or to re-locate the existing ones.
IMHO, ignore the conduit as an earth, and run earth wires through it where it's in suitable places to be re-used.
Remove the old boxes and replace with modern ones. What conduit you end up re-using will then simply be a convenient and well protected run for modern cable, but with no electrical function.. It might well save some time for lighting switch drops.
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